Ordinal numbers give the "order" in which something occcurs: first, second,
etc. Ordinals exist for all numbers, but normally only the forms from one
to ten are used in Spanish:

primero

first

sexto

sixth

segundo

second

séptimo

seventh

tercero

third

octavo

eighth

cuarto

fourth

noveno

ninth

quinto

fifth

décimo

tenth

These are adjective forms, so the usual endings are used, depending on the
noun modified: -o, -os, -a, -as. In addition,
note the special shortened forms primer and tercer, used before
masculine singular nouns: mi primer examen. The ordinals are most
frequently used before nouns, but may appear afterwards, especially with
names. After names, the word "the" is omitted in Spanish.